Always bring at least two plastic cards with you - for example, a Visa and a Master Card. Bring your bank's "express/emergency" service phone number with you, in case your credit card is stolen or lost. Keep your phone numbers separated from your cards.
Also bring a small sum of US Dollars in case of emergency. These should not be spend at random but are always good to have if everything else fails. Spread them out so you don't lose them in case of robbery or theft. If you end up without a credit card and no cash supply at all, you can have money wired through services such as Western Union. It's quite expensive and usually a bad idea but as a last resort it may prove a welcome lifeline.